WEEKLY WHINE

Do-it-yourself astronomy

There was to be a Telescope Night on Campus last night, but it was cloudy. Thus, we will have Telescope Night on Campus tonight instead. Mars is currently at opposition. It's at a magnitude of -1.7, brighter than Sirius. Usually not as bright, now it is. Its angular size has increased to 16.2 arcseconds, which is pretty big, almost the size of Saturn. On a remarkably clear night, its surface features are plainly evident. Tonight will not be such a good night mainly because we are in the midst of the LA basin. The atmosphere here tends to be warm, polluted, and ultimately, turbulent. There are many better places to observe, but the fun of Telescope Night on Campus is that it's on campus.

Astronomers like to travel to places like Hawaii, Arizona, or even Chile to do their observing, which makes people think that it's not as much fun on the homefront. But it is; anybody can enjoy the skies. A four-inch telescope is enough to see good views of the planets, multiple stars, and clusters. Some nebulae and galaxies also look quite good in a four-inch, but a Barlow lens, which increases the eyepiece's magnification by a factor of 2 or perhaps 3, is also beneficial. For even more light gathering power, try a six-inch or an eight-inch. Eight inches tends to be the largest diameter mirror that yields good images without becoming too expensive for the average person.

With an eight inch telescope, styles begin to be more important. Newtonians aren't that great at eight-inch sizes; the better solution is the Schmidt-Cassegrain telescope [SCT]. This is the style with the hole in the primary mirror, through which the secondary mirror reflects the light. This is a good way to make compact telescopes that still have a good focal length. The other common style for an eight-inch is the Dobsonian, which is similar to a Newtonian but has a longer focal length and comes in a base instead of on a tripod. Dobs are longer but depending on the tube, they may turn out lighter than their SCT relatives. Caltech SEDS uses two 8" SCT telescopes, both of which are fairly heavy. Generally, it takes two people to carry the case and another for the tripod. When we finish our Dobsonian, it should be of a weight that's reasonable for two people.

There are many popular observational targets for backyard telescopes. Foremost among them is probably the Orion Nebula. Located at about 5h 35m -5° 30', M42 [NGC 1976] is a place frequented by amateurs. Four bright stars, known as the Trapezium, illuminate this area of rapid star formation located about 1500 ly away. HST, of course, picked up some good pictures of one part of the Nebula several years ago. Orion has many other notable features, such as its two bright stars, Betelgeuse and Rigel. Betelgeuse is a red supergiant that is the largest known star. Tagged α Ori [that's alpha Orionis], it's tenth in brightness. Seventh brightest is Rigel, in the opposite corner of Orion the Hunter from Betelgeuse. It also bears a distinctive hue, something of a blue-white. β Ori is actually a double star, but the second one is hard to see, overwhelmed by Rigel itself. Other deep sky objects are fun to see as well. There's IC 434, a nebulaic formation containing the well-known Horsehead Nebula. It consists of a reddish emission nebula blocked by an absorption nebula in front of it that just happens to have the shape of a horse from where we are. You'll find that south of ζ Ori.

More fun things to see include the Dog Star, the aforementioned Sirius in Canis Major the Big Dog. Designated α CMa, it brings with it a magnitude of -1.46, brighter than any other star other than the Sun. Several thousand years ago, it was actually a summer star rather than a winter star. Even now we discuss the dog days of summer. A short swing around the sky takes us to Leo the Lion, radiant of the Leonid meteor shower. SEDS, of course, took a trip to Joshua Tree to see that shower last November. Its big huge peak cycles about every 33 years. That means that this year's shower is expected to be even better.

Much is made of nebulae, but star clusters are often just as great. As an example, try M13 [NGC 6205], the Great Cluster of Hercules. It is situated at 16h 42m +37°, on the right side of a structure called the Keystone of Hercules. It's a globular cluster, one containing stars arranged quite nicely in a sphere. The most popular galaxy, then, is the Great Galaxy of Andromeda, catalogued as M31 [NGC 224]. You can find it at 0h 45m +41°, next to ν And. It travels with two companion galaxies, M32 [NGC 221] and M110 [NGC 205]. Some folks will tell you that Messier's catalogue didn't run up to 110. He went up to about 103 and later added seven more. Of course, it's interesting to note that Charles Messier was actually a comet hunter. His catalogue contained objects that he frequently thought were comets, so he enumerated them to avoid looking at them. Now, most amateur astronomers like to avoid not looking at Messier objects.

For those in the south, try looking at the Gum Nebula. It hasn't been catalogued simply because it's big. It extends about 35° across the sky, present in the constellations Vela the Ship's Sails and Puppis the Ship's Stern. By the way, the "ship" referred to is Argo Navis the Ship. It's the ship Argo of Jason and his Argonauts. Argo Navis is no longer a constellation; it's large enough to have been subdivided into four parts: Vela the Ship's Sails, Carina the Ship's Keel, Puppis the Ship's Stern, and Pyxis the Ship's Compass. The Gum Nebula is in the Sails and the Stern; it's named after Colin Gum, who discovered it in the first place. This nebula contains a central area powered by a pulsar, PSR 0833-45. It also operates an X ray source, Vela X.

The sky is loaded with fun things to see, and it can be scanned even with a little set of binoculars. The naked eye is also useful if the sky is dark enough. Around here it isn't.